LC-1 says way rich but idle is right

jamesawooten · Post by **jamesawooten** » Tue Feb 21, 2006 7:46 am

Hi All,

I'm having a problem understanding the mixture readings I'm getting at idle. The LC-1 (both in logworks and in Megatune) says that the mixture is at 11.8-12.6, but my ear says that it is about right - if I decrease the VE entry enough to get the mixture to 13.2, the motor starts to hunt and die, indicating a too lean condition.

I've done several free-air calibrations and even reset the unit to perform it's initial heater calibration as well with no effect.

Any ideas?

Jim Wooten

wes kiser · Post by **wes kiser** » Tue Feb 21, 2006 9:26 am

Are you sure you have the right fuel type set in the configuration stuff for the lc1? If it thought you were running a fuel with a lower stoichemtric a/f ratio, then it would read "rich". I know with my lm1, sometimes the settings would get changed, and I wouldn't have done it intentionally.

jamesawooten · Post by **jamesawooten** » Tue Feb 21, 2006 9:59 am

Hmmmm, it said 14.7 Gasoline last time I looked - haven't touched that one. I'm going to pull it out of the manifold as soon as I get home this evening and do a free air calibration and then watch with logworks to verify it reads 20.9 in air before sticking it back in there.

mops · Post by **mops** » Tue Feb 21, 2006 11:09 am

AFAIK, idle haunting is not a result or running lean at idle. my car idles just fine between 11:1 to 16:1 afr.

they key thing is all bins around idle point should be reasonably flat - that will fix haunting. aswell make sure timing is are pretty flat. In most cars idle timing should be between 10 and 15 degrees.

good idea is aswell to incerase bins below idle point (both rpm and map), so as the car falls below idle, it will recover faster....

depending on the engine you have, ou engine might need 13:1 to idle properly... which means you are not much off...

wes kiser · Post by **wes kiser** » Tue Feb 21, 2006 11:57 am

It will read 20.9 whether you have the right fuel selected or not (that is percent oxygen). What does your lambda reading say when it is running 11:1? For instance, if gasoline was selected as the fuel, lambda would read 11/14.7=.75. There is a chance your engine just likes to idle that rich I suppose (can't imagine that though). How much timing are you running around idle and what kind of engine is it?

jakobsladderz · Post by **jakobsladderz** » Tue Feb 21, 2006 1:38 pm

When I had my idle ignition timing set around 25-30Â° I could not get my engine to idle stoichiometric, it would die leaner than about 13:1 (petrol). When I dropped the timing to 10Â°, it now idles happily at 14.7:1 and will continue idling all the way to 16.5:1 (with the odd missfire). I found the same thing on two different engines (mitsu 4G63 2li and mitsu 4G54 2.6li) with standard cams on them. If you are running a lumpier-than-usual cam you may not be able to get it to run happily with that little amount of timing or fuel, so you're forced to run rich..

jamesawooten · Post by **jamesawooten** » Tue Feb 21, 2006 3:39 pm

Hi Guys,

Thanks for all the responses. The motor is a Toyota 4AGE 20V silvertop with individual throttle bodies. We are running MSII and V3.0, with the MSII directly driving the original coil. VR input is from the original distributor (dizzy to you guys down under) with all but 4 teeth removed from the NE wheel.

The ignition timing may be part of the issue. Our IAC installation isn't working (don't ever think an ND IAC will work the same as a Bosch IAC) and the measurements I've been making were at about 1500-1600 rpm with about 26 degrees of advance.

This evening I've capped off the IAC, and adjusted the throttle bodies to give me a 900-1000 rpm idle and reset everything from idle to 1800 rpm to 16 degrees of advance to eliminate that from the equation for a while.

Unfortunately, I seem to have gotten myself into a new problem in messing around with the LC-1. We had changed the lamda sensor type several times in the configurator and created new table entries repeatedly and now the O2 display seems almost frozen - way too steady like an immense amount of smoothing or very little sampling is taking place.

I've returned the values in the configurator to the original and even completely reinstalled and reconfigured MegaTune, but the lack of response still seems to be there. The next step (I guess) is to re-flash the MS and reload the files.

Incidently, I did a free air calibration of the LC1 and observed 20.9 in free air. Reinstalling and watching with logworks showed good response of the sensor.

mops · Post by **mops** » Tue Feb 21, 2006 3:52 pm

ok, logworks expects output of 0V=7:1 afr (about that ) and 5V = 25.5: AFR (about that).

how, if you configure it correctly for megasquirt you should have reconfigured the sensor to 0v=10 afr and 5v = 20 afr.

thats why logworks reposrts 20.8 in free air (with default config it reports 25 afr in free air).

lm programmer has smoothing option thats configurable, amke sure it's all good there.

make sure no input smoothing is set in megatune (in ms2 you set all smoothing values to 100 to disable smoothing/lagging)

jamesawooten · Post by **jamesawooten** » Wed Feb 22, 2006 4:12 am

Well, I woke up this morning knowing why my output seemed so crazy. Somehow, in all my messing around, the output that I was using on the LC-1 got reset back to it's default of emulating a narrow band sensor. Duh! I hate it when I do stoop things like that.

I'm going to re-wire the connector this evening to use Analog 2 instead of Analog 1 which is what I should have done in the beginning if I had actually read the LC-1 manual BEFORE wiring up the connector......

I've also seen some posts stating to use a 470 ohm resistor between the output and the MS. Should I do that as well while I'm messing around?

Regards,

Jim Wooten

mops · Post by **mops** » Wed Feb 22, 2006 10:43 am

never heard about it. i run without resistor. in lm programmer make sure the you have a tick in 'high impedanze input' or something like that.